The present invention relates to a delivery blood storing member-equipped blood reservoir tank that is equipped with a delivery blood storing member for temporarily storing blood and delivering stored blood in an extracorporeal blood circulation circuit for use with, for example, an artificial lung or the like. The invention also relates to a blood delivery instrument for an extracorporeal blood circulation circuit provided downstream from the blood reservoir tank.
Heart surgery often uses an extracorporeal blood circulation circuit having incorporated therein an artificial lung for removing carbon dioxide from blood and adding oxygen to blood instead of the living lung. The extracorporeal circulation circuit is to drain blood from the patient's vein, subject the blood to gas exchange in the artificial lung, and return the blood to the patient's artery. The extracorporeal circulation circuit also includes a cardiotomy line for sucking in blood from the operation area, removing foreign matter therefrom, and returning the blood.
In general, the extracorporeal circulation circuit with an artificial lung includes a blood tank for temporarily storing blood drained from the patient and a cardiotomy reservoir for filtering blood sucked from the operation area and temporarily storing the blood. The blood tank and cardiotomy reservoir serve a buffering function of adjusting the amount of blood in the circuit and maintaining a constant amount of blood returned to the patient.
There is a situation that the volume of blood in the blood tank becomes zero during extracorporeal blood circulation. If the blood feed pump continues to operate, air can be fed into the extracorporeal circulation circuit. To avoid such inconvenience, the tank is provided with a level sensor for monitoring the volume of blood in the tank. When the sensor detects that the volume of blood in the tank is below a predetermined value, the feed pump is interrupted to stop blood delivery action until the volume of blood in the blood tank is restored. The temporary interruption of blood delivery, however, is undesirable because it causes blood stagnation throughout the circuit including the artificial lung.
Therefore, there is a need to provide a delivery blood storing member-equipped blood reservoir tank capable of changing the flow of blood delivery in accordance with the amount of blood stored if the amount of blood stored in the blood reservoir tank becomes equal to or less than a predetermined value, and a blood delivery instrument for an extracorporeal blood circulation circuit disposed downstream from the blood reservoir tank.
It is a first object of the invention to provide a delivery blood storing member-equipped blood reservoir tank and a blood delivery instrument for an extracorporeal blood circulation circuit that, if the amount of blood in the blood reservoir tank becomes equal to or less than a predetermined value, are able to reserve an amount of blood in sensitive correspondence to the amount of blood stored.
It is a second object of the invention to provide a delivery blood storing member-equipped blood reservoir tank and a blood delivery instrument for an extracorporeal blood circulation circuit wherein the delivery blood storing member, which is pressed for blood delivery, is prevented from being damaged.
It is a third object of the invention to provide a blood delivery mechanism-equipped blood reservoir tank that considerably reduces the incidence of air bubbles that can be formed due to collision between a surface of the blood stored in a blood storing portion and an incoming blood current when blood delivery based on a blood delivery flow corresponding to the amount of blood stored in the blood storing portion is performed after the amount of blood in the tank blood storing portion has decreased to or below the predetermined value, and when the amount of blood stored increases back to or above the predetermined value.
It is a fourth object of the invention to provide a blood delivery mechanism-equipped blood reservoir tank that considerably reduces the damages to a delivery blood reserving portion that may be caused at the time of blood delivery.
It is a fifth object of the invention to provide a blood delivery mechanism-equipped blood reservoir tank that is equipped with a blood delivery driving unit for pressing a delivery blood reserving member, wherein even if the blood delivery driving unit is designed to press the delivery blood storing member by expansion of a blood reserving member-pressurizing portion formed of an expandable sheet material, the blood reserving member-pressurizing portion does not affect the delivery blood reserving member when the blood reserving member-pressurizing portion is not expanded, so that when the amount of blood in a blood storing portion becomes equal to or less than a predetermined value, the delivery blood reserving member reserves amounts of blood in sensitive correspondence to the amount of blood stored.
Lately, the conveyance of blood into the blood reservoir tank and the drainage of blood from a patient are often performed by a method using a suction device (negative pressure applying device) connected to the blood reservoir tank. When this device is operated, the pressure in the blood reservoir tank portion becomes negative, and the negative pressure affects the interior of the delivery blood reserving member. That is, the delivery blood reserving member becomes exposed to a negative pressure inside the member due to the operation of the suction device (negative pressure applying device), while receiving the atmospheric pressure on the outside. Therefore, the delivery blood reserving member is pressed by a differential pressure between the inside and outside pressures, so that the liquid surface-sensitive (pressure-sensitive, pre-load-sensitive) function of the delivery blood reserving member may be impeded.
It is a sixth object of the invention to provide a blood delivery mechanism-equipped blood reservoir tank that will not impede the liquid surface-sensitive (pressure-sensitive, pre-load-sensitive) function of a delivery blood reserving member even if a suction device (negative pressure applying device) is connected to the blood reservoir tank.